The present disclosure is related to downhole power generation systems and, more particularly, to drill bit including devices that generate electrical power.
A wide variety of downhole well tools that require electrical power for operation are used during exploration and production of subterranean hydrocarbons. For example, flow control devices, sensors, samplers, packers, instrumentation within well tools, telemetry devices, and well logging devices are each regularly used and require electricity in performing their respective functions. One common method of supplying electrical power to downhole well tools is to use batteries that can be disposed within the downhole well tools. Unfortunately, some batteries cannot operate for an extended period of time at downhole temperatures, and those batteries that are able to operate in downhole temperatures must still be replaced periodically.
Another common method of supplying electrical power to downhole well tools is extending one or more electrical lines from the surface to the downhole well tools. Electrical lines that extend for long distances downhole, however, can interfere with flow or access if they are positioned within a tubing string, and they can be damaged during run-in if they are positioned outside of the tubing string or cumbersome to deal with when moving pipe in an out of the hole. In addition, rotating such drill strings can result in the need for slip rings to jump the power from a non-rotating part of the drilling system to a rotating part. Such slip rings are often unreliable. Yet another common method to supply power down hole is through the use of a turbine-powered generator positioned in the mud flow, where drilling fluid passes through the turbine, which spins a generator shaft to produce power.
Recently, sensors and other electricity-consuming devices have been placed directly in drill bits of downhole drilling systems to provide various functions, such as monitoring and reporting data relating to the drill bit, the drilling operation, and the surrounding formation being penetrated by the drill bit. It is often difficult to supply electrical power to such electricity-consuming devices from above the drill bit because of the presence of the mechanical connection between the drill bit and the remaining portions of the drill string. Therefore, batteries are often used to power drill bit-mounted devices. As can be appreciated, the electrical energy provided by batteries is often limited due to their size and capacity.